Let me tell you what I'm going to do and you tell me if it sounds right.  I'm going to put two 270w panels in series, with a Vmp of 36.40V a piece, with voltage in series of 72.8V;  Imp is 7.42A.

I'm going to have a combiner box for future expansion it will be approximately 35-45' depending on how I run it from panel to combiner box, so I'm going to use #10 wire. From the combiner box to the charge controller it will be 30-35' and I will be using #8 wire. 

Is this good enough? The most new panels I'll ever add would be to put two more in series,  so then from the combiner box to the controller it would be 72.8V at 14.84A. Thanks
Steve  

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I thinks it sounds good. This is the same system we've discussed in the previous thread, right?

https://www.greentechrenewables.com/article/conductor-sizing-voltage-drop

Are you using conduit? or are you burying the wire run? It's good to avoid heating (due to sun) as much as possible.

Also, especially for battery systems, consider less than 2% (or even 1%) voltage drop. In your case, it looks like it satisfies. I'm looking forward to seeing the photographs of the installation.

leventbas,

Thanks for the help.  When I gave you the distances between the module and the combiner and the combiner and the controller, that was actuall distance.  Because I have a plus and a minus wire, would I double it when calculating distances. Is that correct?  If so, are the wire sizes I indicated in my last post O.K.?

I can figure what size wires I need from my panels to the combiner box by using distance, amperage, and wattage.  From the combiner box to the controller I can up my amperage after it is increased at the combiner box and then figure the distance from the combiner box to the controller and size the wire appropriately. Where I'm confused is when you say I have to add these two runs together.  I'm maybe just not understanding you.  Lets use this example:  If I have two runs coming in to the combiner box in parallel, each runs wire is sized appropriately for the distance between the module and the combiner box.  Now at the combiner box the amperage will double and the voltage will stay the same so I will increase the wire size from the combiner box to the controller, taking into consideration voltage, increased amperage, and the distance between the combiner box and the controller, forgetting about the distance from the module to the combiner box.  Have I got this right or am I just dumber then a post?

Steve

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12 years 11 months ago
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Steve Seglem
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